1. Field of the Invention
The present invention relates to an airbag apparatus for a vehicle for protecting a person in a vehicle such as an automobile; for example, a driver or a passenger sitting in the front passenger seat, from impact upon head-on or side collision of the vehicle, to thereby ensure safety of the person. More particularly, the invention relates to an airbag apparatus for a vehicle configured such that upon inflation and deployment of an airbag, a portion of an interior panel surrounded by a fracture groove for fracture opening is ruptured along the fracture groove to thereby enable the airbag to inflate and deploy to the outside (front side) of the interior panel.
The term “fracture groove” used in relation to the present invention refers to a weakened portion or a fracture portion for fracture opening which is composed of successive holes formed on the reverse or inside surface of an interior panel of a vehicle through irradiation with a laser beam generated from laser generation means in the form of laser pulses, or a groove continuously or intermittently formed on the reverse or inside surface of the interior panel by use of a cutting tool or the like.
2. Description of the Related Art
There has been known an airbag apparatus for a vehicle for protecting a person in a vehicle such as an automobile; for example, a driver or a passenger sitting in the front passenger seat, from impact upon head-on or side collision of the vehicle.
Such an airbag apparatus includes an airbag, an airbag case for accommodating the airbag folded such that the airbag can easily inflate and deploy, and an inflater for inflating the folded airbag within a short period of time. In particular, an airbag apparatus which is used for the front passenger seat of an automobile is disposed behind an interior panel of the automobile. When the automobile decelerates suddenly because of, for example, a collision, the inflater is operated so as to rapidly inflate the airbag, to thereby rupture and open the interior panel along the fracture groove and cause the airbag to inflate and deploy toward the outside of the interior panel through the opening. Thus, the airbag apparatus protects the passenger from impact of the collision.
The fracture groove for causing the airbag of the airbag apparatus to inflate and deploy toward the outside of the interior panel are formed by forming successive small holes on the reverse surface of the interior panel through irradiation with a laser beam (see, for example, Japanese Patent Application Laid-Open (kokai) No. 2004-1677).
A conventional airbag apparatus for a vehicle will be described with reference to FIGS. 1 to 3.
FIG. 1 is a vertical cross sectional view of a main portion of a conventional airbag apparatus for a vehicle; FIG. 2 is a plan view of the main portion; and FIG. 3 is a vertical cross sectional view showing operation of the airbag apparatus when the airbag is inflated.
As shown in FIG. 1, an airbag apparatus 1 for a vehicle includes an interior panel 2, an airbag 3, an airbag case 4, a frame 5, a pair of reinforcement members 6, an unillustrated inflater, etc.
The interior panel 2 is attached in front of the front passenger seat of a vehicle; e.g., an automobile, and is formed of a synthetic resin material, such as polypropylene. Further, when necessary, the outer surface of the interior panel 2 is covered with a surface layer.
As shown in FIGS. 1 and 2, a fracture groove 7 is formed on the reverse surface of the interior panel 2 so as to form an opening 8 (see FIG. 3) when the. airbag apparatus is operated, to thereby enable the airbag 3 to inflate and deploy to the outside of the interior panel 1 through the opening 8.
As shown in FIGS. 1 and 2, the fracture groove 7, which forms a laterally elongated rectangle of a size corresponding composed of hinge-side fracture groove sections 7a and 7b corresponding to the two longer sides of the rectangle, side fracture groove sections 7c and 7d corresponding to the two shorter sides of the rectangle, and a center fracture groove section 7e extending between the side fracture groove sections 7c and 7d in parallel with the hinge-side fracture groove sections 7a and 7b. The fracture groove sections 7a to 7e enable the rectangular region surrounded by the fracture groove sections 7a to 7e to be ruptured and opened in the manner of a casement (i.e., French window).
The fracture groove sections 7a to 7e are formed by forming successive small holes (blind holes) on the reverse surface of the interior panel 2 through irradiation with an infrared laser beam having a beam diameter of 0.2 to 0.5 mm and a wavelength of 10.6 μm, in such a manner that the small holes do not pass completely through the interior panel 2.
The frame 5, which assumes a rectangular tubular shape, is bonded, by means of vibration welding or any other suitable process, to the reverse surface of the interior panel 2 via a flange portion 5A of the frame 5. The frame 5 is formed of a synthetic resin material, and extends along the rectangular fracture groove 7 so as to surround the groove.
The pair of reinforcement members 6, formed of a synthetic resin material, are attached to the inner wall surface of the frame 5, and are bonded to the reverse surface of the interior panel 2 so as to reinforce a portion of the interior panel 2 surrounded by the fracture groove 7.
Each of the reinforcement members 6 includes a support portion 6a a coupled with the inner wall surface of the frame 5 via a dovetail, and a reinforcement portion 6c bendably connected via a hinge portion 6b to the upper end of the support portion 6a and bonded, by means of vibration welding or any other suitable process, to the reverse surface of the portion of the interior panel 2 surrounded by the fracture groove 7.
The airbag 3 is accommodated within the airbag case 4 formed from a metal plate in a folded condition as shown in FIG. 1.
A plurality of hooks 9 are provided on the side wall portions of the airbag case 4 in the vicinity of an upper end opening 4a thereof such that they project outward. The hooks 9 are engaged with holes 6d in the support portions 6a of the reinforcement members 6 and holes 5b formed in the frame 5 to correspond to the holes 6d, whereby the airbag case 4 is secured to the frame 5.
An inflator accommodation portion 10 is provided at the lower end of the airbag case 4 so as to accommodate an inflater (not shown) for supplying an inflation gas to the airbag 3. The airbag case 4 is fixed to a stationary member, such as a cross member 12, via a support member 11 and by means of a bolt and nut 13.
The thus-configured conventional airbag apparatus vehicle, an impact force caused by the collision is detected by an unillustrated sensor. A control unit including a CPU judges whether or not the detected impact force is equal to or greater than a predetermined value. When the control unit judges that the impact force is equal to or greater than the predetermined value, the control unit issues a signal for causing the inflater to generate a high-pressure gas. The gas is fed to the airbag 3 so as to promptly inflate the airbag 3. The inflating airbag 3 presses, from inside, the portion of the interior panel 2 surrounded by the fracture groove 7. As a result, the center fracture groove section 7e, the side fracture groove sections 7c and 7d, and the hinge-side fracture groove sections 7a and 7b are fractured, whereby the portion surrounded by the fracture groove 7 is divided into two fracture-opening subsections 2A and 2B. The fracture-opening subsections 2A and 2B are separated from the interior panel 2, and are opened in the manner of a casement as shown in FIG. 3, while being turned about the hinge portions 6b of the reinforcement members 6. As a result, the airbag 3 inflates and deploys to the outside of the interior panel 2 via the opening 8, which is formed through opening of the fracture-opening subsections 2A and 2B. Serving as a cushion, the inflated airbag 3 supports the passenger at his/her chest or head, thereby protecting the passenger from the impact force of collision.
However, the above-described conventional airbag apparatus for a vehicle has the following drawback. In a state where the fracture-opening subsections 2A and 2B are opened in the manner of a casement as shown in FIG. 3, a rupture edge 2A1 of the fracture-opening subsection 2A along the hinge-side fracture groove section 7a and the distance L1 between the rupture edge 2A1 and a welding rib 6c1 of the reinforcement portion 6c of the corresponding reinforcement member 6 are relatively long. Similarly, a rupture edge 2B1 of the fracture-opening subsection 2B along the hinge-side fracture groove section 7b and the distance L2 between the rupture edge 2B1 and a welding rib 6c1 of the reinforcement portion 6c of the corresponding reinforcement member 6 are relatively long. Therefore, when the fracture-opening subsections 2A and 2B are opened in the manner of a casement as shown in FIG. 3, the rupture edges 2A1 and 2B1 of the fracture-opening subsections 2A and 2B abut against the surface of the interior panel 2 to thereby limit the open angles of the fracture-opening subsections 2A and 2B. That is, as shown in FIG. 3, the open angles of the fracture-opening subsections 2A and 2B are limited such that the fracture-opening subsections 2A and 2B incline toward each other. Therefore, when the inflation pressure of the airbag 3 acts on the inclined fracture-opening subsections 2A and 2B when the airbag 3 inflates toward the outside of the interior panel 2 via the opening 8, the welding ribs 6c1 of the reinforcement portions 6c may separate from the fracture-opening subsections 2A and 2B, or cracks may be generated in corresponding to the welding ribs 6c1, so that portions of the fracture-opening subsections 2A and 2B extending from the cracks over the distance L1 and L2, respectively, may break and scatter as indicated by imaginary lines in FIG. 3.
Moreover, since the open angles of the fracture-opening subsections 2A and 2B are limited such that the fracture-opening subsections 2A and 2B incline toward each other, the inflation of the airbag 3 toward the outside of the interior panel 2 is restricted.